JPS60202119A - Resin composition and laser marking thereof - Google Patents

Abstract

PURPOSE:A resin composition which, when laser-marked, can give clear, legible, marked characters, prepared by adding a specified amount of carbon black to a specified resin composition. CONSTITUTION:A resin composition prepared by adding 0.5% or above carbon black to a principal component comprising 10-20wt% novolak epoxy resin, 10- 20% phenol novolak resin or cresol novolak resin and 60-80wt% inorganic filler. The marking of a resin-sealed semiconductor device has been conducted by using a thermosetting ink and, therefore, there has been a problem that the marked characters are thinned down by rubbing in the subsequent steps or during handling in packaging or by swelling during solvent washing. Although laser marking is effective in respect of resistance to detachment of marked characters and the index-up of a marking step, it is not yet put into actual use because the marked characters are not legible. By using the resin composition containing carbon black in an amount increased within the scope not detrimental to the function as an electrical insulating material, clear and legible marked characters can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of the Invention) The present invention provides a resin composition suitable for encapsulating semiconductor devices and capable of providing clear display by laser marking, and a laser marking method using the resin composition. be.

(Prior Art) Conventional resin-sealed semiconductor devices have been stamped using thermosetting ink. That is, after cleaning the resin surface of the encapsulated semiconductor device with an organic solvent or the like, epoxy resin, white,
8 After transferring and stamping the company name abbreviation, product name, lot number, etc. onto the resin surface with thermosetting ink made of silvery white pigment etc.
It was stored in a constant temperature bath at 0 to 120°C to be thermally cured and baked onto the resin surface.

Semiconductor devices stamped by this method have problems such as being rubbed during handling during post-processing and mounting, or swelling due to solvent cleaning, making the stamped characters difficult to see. On the other hand, recently, the introduction of a laser marking device is being considered as a marking method to improve such problems. Laser marking is a method in which a laser beam is irradiated onto the surface of the resin coating to carve out the resin and make a mark. Although it is very effective in reducing the difficulty in removing printed characters and increasing the index in the stamping process, it has not yet been put into practical use because the printed characters are difficult to see and difficult to distinguish.

(Object of the Invention) An object of the present invention is to provide a resin composition that can provide clear and easily visible stamped characters when laser marked.

(Structure of the Invention) The present invention focuses on the fact that carbon black, which has been conventionally mixed as a coloring agent in epoxy resin compositions, absorbs laser light well, and uses carbon black as an electrical insulating material to the maximum extent possible without impairing its function. The present invention provides a method for producing a resin composition whose weight has been increased to 100% and then laser marking a product using the resin composition.

(Examples) The present invention will be explained in more detail below based on Examples.

Table 1 is a table showing blending examples of an embodiment of the present invention and a conventional resin composition. FIG. 1 is a graph showing carbon content and volume resistivity across the examples of the present invention and conventional products, and FIG. 2 is a graph showing the depth of stamped characters.

Table 1 Examples of the present invention and methods for producing conventional epoxy resin compositions are described below. First, an intermediate mixed according to the composition shown in Table 1 is prepared.

Other additives listed in Table 1 include mold release agents such as carnauba wax and synthetic wax, coupling agents for fused silica (filler) and microwave ingredients such as epoxin run, and antimony trioxide (flame retardant). , imidazoles as curing accelerators. 80~
The mixture is put into a mixing roll controlled at 100°C, heated and melted, and kneaded uniformly. After cross-crossing, the intermediate is cooled to room temperature and pulverized using a hammer mill or the like. The pulverized powder is molded into an appropriate weight to form a resin composition.

This manufacturing method itself can be carried out using conventionally used equipment and manufacturing conditions.

Using this epoxy resin composition, a lead frame wire-bonded to an external lead to which a semiconductor element is attached is sealed with a resin by transfer molding. Transfer molding can also be performed using the same equipment and under the same conditions as conventional methods. ζThe abbreviation of the company name is printed on the resin surface of the semiconductor device manufactured in this way.

The product name, manufacturing lot number, etc. are stamped using a laser marking device. Laser marking is performed by placing a mask designed to transmit the laser light onto the characters to be stamped on the W resin surface and blocking other areas, and then irradiating the laser light focused by a lens from above. Let's do it. The laser beam suitable for such resins has a wavelength of 1.06 μm.
This is a YAG laser.

(Effects of the Invention) FIG. 2 compares the legibility of printed characters on semiconductor devices sealed with the resin compositions shown in Table 1. In the conventional product, the depth of the stamped characters is about 2 to 6 μm, and the characters are dark gray.

Since the resin surface in the background is black, it is extremely difficult to read.

On the other hand, in Examples 1, 2, and 3, as the carbon black content increases, the depth of the printed characters becomes deeper and the characters become bright white, and the contrast with the background resin surface is improved.

Among the compounds contained in the resin composition, laser light (wavelength: 1.06 μm) is easily absorbed by carbon black. For this purpose, it is thought that the carbon black itself is oxidized and blown away, and the surface of the fused silica and resin are roughened to whiten the printed characters. Therefore, the higher the carbon black content, the better. However, if the carbon content is too large, the volume resistivity of the resin composition, which is originally an insulator, will decrease. FIG. 1 shows the relationship between carbon content and volume resistivity. According to Figure 1, the upper limit is 5%;
%, the volume resistivity decreases significantly. In addition, for applications requiring high insulation, it must be kept below 5%.

In any case, in Examples 1, 2, and 3 of the present invention, conventionally,
This facilitates the adoption of laser marking methods, which have been difficult to put into practical use due to the difficulty of seeing the printed characters.

According to the present invention, the "fading" and "dropping" of characters, which were the drawbacks of conventional marking methods using thermosetting ink, do not occur at all, and clear stamping is performed, which improves the quality of resin-sealed semiconductor devices. It has contributed greatly.

[Brief explanation of drawings]

FIG. 1 is a graph comparing the volume resistivity of a conventional product and an example of the present invention. FIG. 2 is a graph comparing the stamping states of the conventional product and the embodiment of the present invention.

Claims (1)

[Claims] (11 novolac type epoxy resin 10 to 20%, phenol novolac resin or cresol novolac resin 10%
20%, 60 to 80% of inorganic filler as main components, and further contains 0.5% or more of carbon filler. (2) 10 to 20 units of novolac type epoxy resin, 1 part of phenol novolac resin or Talesol novolac resin
1. A method for laser marking a resin composition, the method comprising laser marking a resin composition containing 0 to 20% as a main component, 60 to 80% of an inorganic filler, and 0.5% or more of carbon black.